If it's calcium carbonate, just dissolve it!

Use muriatic acid to lower your pH to 7.0, and then add just a little more acid. Keep it at 6.8 - 7.0 for a couple of days -- if it doesn't dissolve, it's not calcium. Actually, with a TA=80 and a CH=40, I'm skeptical that it's calcium . . . unless you saw it turn cloudy, immediately after adding both.
Read http://pool9.net/muriatic/

Also, if you can see your pool return, do the DE test: http://pool9.net/de-test/ . (But there's no use, unless you could see a white cloud emerging from the nozzle.)